Sebastian Vettel can become Formula One's youngest triple champion without scoring a point in Monday's (NZT) season-ending Brazilian Grand Prix but Fernando Alonso has a more sensational script in mind.

If Ferrari's Alonso retires from what promises to be a nail-biting race at Interlagos, the title will go to his Red Bull rival there and then - just as it will if the Spaniard fails to finish in the top three.

The odds favour 25-year-old Vettel, who has a 13-point lead, but Formula One has a habit of ripping up comfortable predictions and turning the seemingly inevitable into the incredible.

Alonso will never give up hope and Vettel will be taking nothing for granted.

"Maybe on paper that chance is not so big, maybe 25 per cent. But deep down, I feel it's much more than that." Alonso, who won both his previous titles in Brazil, said after last weekend's US Grand Prix.

The statistics show that Vettel need only do what he has done 13 times so far this season - finish fourth or higher - to take the crown for a third year in a row even if Alonso dominates the race.

Bookmakers offer odds of 1/6 on the Red Bull driver for the title with Alonso at 4/1.

The odds simply reflect the reality that Vettel has finished his last six races on the podium, winning four of them in a row. But what gives hope to Ferrari fans is what happened in the six races where Vettel was not in the top four.

RELIABILITY WORRIES

If the results from Monza, Hockenheim, Valencia or Malaysia were to be repeated on Sunday then Alonso would end up champion. In two of the three races Alonso has won this year, Vettel failed to score.

Also in the Spaniard's favour are the key factors of reliability and weather.

Interlagos, a wonderfully ramshackle cauldron of motor racing passion and romance, has seen race strategies blown apart by torrential rain and blazing sunshine sometimes in the space of half an hour.

Alonso's Ferrari has had the sort of reliability a tractor driver might expect while Vettel's Red Bull team have suffered costly alternator failures including one last Sunday to Mark Webber.

"Reliability is a concern," Red Bull technical head Adrian Newey conceded in Austin, even if engine provider Renault believe they have fixed the problem. "It is unfortunately our third alternator failure this year which is a ticking time bomb.

Vettel will be going flat out for victory on Sunday as his safest option, mindful of the problems drivers have had in the past when requiring only a handful of points.

In 2008, McLaren's Lewis Hamilton left it until the last corner at Interlagos to get the fifth place he needed to beat Ferrari's Felipe Massa to the title. In 2003, Michael Schumacher laboured to eighth place in the Japanese season-ender to beat Kimi Raikkonen to the crown by two points.

Vettel himself took the 2010 title after going into the final race in Abu Dhabi with a 15-point deficit to Alonso while Raikkonen won his 2007 championship for Ferrari at Interlagos after arriving seven points off the lead.

"We go to the last race to fight and take nothing for granted until the last corner," said Ferrari team boss Stefano Domenicali. "I remember in 2008, when we were winning the constructors', at the last corner we lost the drivers'. So I have got still that memory in mind."

The title duel will be the main event but there will be plenty of other storylines as well at the end of an enthralling and highly unpredictable season that started with seven different winners in seven races.

Schumacher will bow out of Formula One, for the second time, at the age of 43 while Hamilton says farewell to McLaren, the only team he has known since his debut in 2007.

Hamilton, having won in Austin, wants to head for Mercedes on a high - and that could also be a big factor in the championship battle. The fierce tussle between mid-table teams fighting for overall positions that translate into millions of dollars may also have an effect.

"For many reasons, this weekend will be a very big race for me," said Hamilton in a team preview.

"As my final race behind the wheel of a McLaren, I vow to the whole team that I'll give it my all on every single lap...I'd love to take victory in Brazil this weekend to give the team the perfect farewell present."